Self guided subjective refraction instruments and methods

ABSTRACT

A refraction device determines a refraction end point to provide corrective optics for a test subject. The device includes an adjustable optical system providing corrective optics to the test subject and an adjustable viewing target disposed along an optical path such as to be viewable through the adjustable optical system by a test subject. The adjustable viewing target includes a directional indicator linked synchronously to at least two choices of corrective optics presented to the test subject.

BACKGROUND OF THE INVENTION

Manifested refraction remains one of the most reliable methods ofarriving at a prescription to correct refractive errors, whether it isused for preparing prescription eyeglasses or contact lenses, or forlaser surgery. However, the current refraction methods have manychallenges, including a steep learning curve, and difficulty inmastering the art, and it typically involves months of practice to learnto produce good prescriptions. Another challenge is that it involvespatient participation. The end point comes after many steps, eachinvolving a forced answer from the patient. The accuracy of each of theanswers determines whether the entire eye test is moving in the correctdirection. A wrong answer may lead the exam down a wrong path. In thecourse of the refraction process, a patient may often ask to repeat thechoices presented to them, because they are not sure or can't decide.Repeating tests and steps in tests often is done to ensure accurateresults. The repeated questioning causes anxiety on the part of thepatient, and the lengthening of the eye exam time. Hence a refractionmethod that can reduce or eliminate patient's requests for repeatpresentations would be desirable and beneficial.

Refraction Testing

The most often asked question in a phoropter refraction test is “Is itbetter one, or better two”, while the conductor of the refraction testflips the lenses to present choice one versus choice two. Once an answeris given by the test subject, the conductor has to know what to do inthe next move. The knowing of the next move takes training, and it is asomewhat long and steep learning curve. In an example of a test using aphoropter, the operator or the conductor of the test would ask “is itbetter one (e.g., at −1.75 D) or better two (e.g., at −2.0 D)?” First,the patient decides which presentation looks better. He or she memorizespresentation one when comparing it to presentation two. He or she mayask: “Can you show me again?” If an answer is finally given, theoperator then selects which lens is to be presented next, i.e., fromtypically extensive training and practice.

In the current state of the art in refraction technology, there are autorefractors, retinal scopes, and wavefront aberrometers. None has thereliability and accuracy that is comparable to a traditional phoropter.Therefore, the outcomes of most objective refraction instrument testsare used as starting points, and not as acceptable final refractionresults. Hence it would be a breakthrough for any refraction technologyto produce results comparable or superior to those of the phoropter, andeven more so if that technology can be conducted by patients with aminimum or no supervision.

A self-guided refraction test would also produce huge economicadvantages. As it is said, the mastering of phoropter refraction isdifficult, and involves months or years to perfect it. A largeproportion of refraction tests are currently performed byophthalmologists or optometrists. These medical professionals typicallyearn a high pay. Therefore, the cost of refraction may be reducedsubstantially if it is performed by a technician, under the supervisionof an eye care professional. The cost may be further reduced, if thetest is performed by the patient under the supervision of a technicianor eye care professional.

A separate computer input panel may be provided for the operator tocontrol the test. That is, a separate person from the test administratormay be enlisted to run the program and use the panel to choose the nextmove in the refraction procedure. It is desired to have a self-guidedrefraction test process.

Over-Minusing

It is also desired to reduce or eliminate over-minus conditions. In apopulation, those persons under the age of 45 generally have eyes withadjustable focal power, or accommodation. During a typical eye exam, aSnellen eye chart viewing target is presented for the patient as theviewing target. Such an eye chart, consisting of letters of varioussizes, typically arranged in a series of rows, is widely used in an eyeexam to guide the doctor to find the optimal lens setting in a devicecalled a phoropter. A patient's ability to read certain lines determinesa measure of the level of quality vision, or visual acuity. Onechallenge during a refraction process is that a patient may often choosea higher negative power, because the letters appear darker and tighter,and are therefore perceived as being “sharper”. A 14 year old patientmay have up to 8 diopters of accommodation power. This over-minusing cancontinue to lead the process down deeper and deeper into the minus powerterritory.

There is an existing mitigation method. It involves the patient“earning” the extra minus power unless the visual acuity is improved atthe more minus power setting. However, this method sometimes fails whenthe patient adapts to the more minus power and rejects the less minusdue to the locking mechanism of the muscle of the eye, that won'trelease the tension. In other words, once a patient is over-minus, it isdifficult to reverse it. Wearing over-minus eyeglasses, patients tend tocomplain about headaches and dizziness, leading to a redoing or aremaking of the lens prescription, which costs lost time and unhappypatients. Hence it is desirable to provide a method that can reduce oreliminate over-minus in a refraction process.

Hence, it is desired to provide a refraction instrument and refractionmethod that reduces or eliminates the over minusing, and is relativelyeasy to learn and easy to perform. It is desired that the instructionsfor such refraction procedure be simple and understandable by mostpeople who are capable of verbal communication, literate or illiterate,and that the instructions are universally applicable to all age groups,and without causing confusion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A) and 1(B) schematically illustrate a directional indicator inaccordance with certain embodiments.

FIG. 2 includes illustrative plots of visual acuity versus sphere power.

FIG. 3(A) schematically illustrates a viewing target for a visual acuitymeasurement including a directional indicator in accordance with certainembodiments.

FIG. 3(B) illustrates a viewing target including a directional indicatorin accordance with certain embodiments.

FIG. 4 include a plot of visual acuity versus axis angle.

FIG. 5 illustrates a process flow in accordance with certainembodiments.

DETAILED DESCRIPTIONS OF THE EMBODIMENTS

A refraction device is provided for determining a visual acuity andproviding corrective optics for a test subject. The device includes anadjustable optical system and an adjustable viewing target disposedalong an optical path such as to be viewable through the adjustableoptical system by a test subject. The adjustable viewing target includesa directional indicator linked synchronously to at least two choices ofcorrective optics presented to the test subject.

The device may include an input device configured to be controlled bythe test subject to indicate a direction suggested by the directionalindicator for selecting between the at least two choices of correctiveoptics. The direction suggested by the directional indicator correspondsto a corrective optics choice as presented to the test subject by theviewing target.

The adjustable viewing target may be adjustable to at least twoconfigurations each uniquely indicative of one of the choices ofcorrective optics.

The directional indicator may include a relatively light dot inside adark area, or vice-versa, a bar or other in-plane rotationallyasymmetric polygon, an arrow, a line, or another in-planerotationally-dependent object, or combinations thereof. The directionalindicator may be configured to be displayed to the test subject in atleast two configurations each uniquely indicative of one of the choicesof corrective optics. The directional indicator may include a white dotinside a black area, such that the white dot is movable to certainpositions each demonstrating a certain direction corresponding to one ofthe choices of corrective optics.

The device may also include a machine coupled with a display andconfigured to adjust the viewing target on the display during a visualacuity measurement of a test subject. A calculator or look-up table, orboth, may be used to determine the visual acuity of the test subjectbased on the visual acuity measurement.

To prevent accommodation, the device may be configured to display for0.4 seconds or less a first corrective optic having more minus spherethan a second corrective optic to be displayed of the at least twochoices of corrective optics. The second corrective optic may bedisplayed after the first corrective optic for longer than the firstcorrective optic, after which the display of the first and secondcorrective optics may be repeated one or more times during the visualacuity measurement.

A refraction method is also provided for determining a visual acuity andproviding corrective optics for a test subject. An optical system may beadjusted to a first configuration for the test subject to view through afirst corrective optic a viewing target including a first directionalindicator. The optical system may then be adjusted to a secondconfiguration for the test subject to view through a second correctiveoptic the viewing target including a second directional indicator. Adirectional input is received, in accordance with the first or seconddirectional indicator, from the test subject uniquely indicating achoice of one of the first and second corrective optics. Based on thechoice, one or more further configurations may be selected for the testsubject to view through one or more further corrective optics for thetest subject to choose until a prescriptive recommendation isdetermined. The prescriptive recommendation may be communicated based onthe choices.

The receiving of the directional input may include receiving a signalfrom an input device controlled by the test subject to indicate adirection suggested by the directional indicator for selecting betweenthe first and second corrective optics. The method may includepresenting to the test subject the choice between the first and secondcorrective optics in accordance with unique directions each suggested bythe directional indicator as corresponding to one of the first andsecond corrective optics.

The directional indicator of the viewing target may be adjusted to atleast two configurations each uniquely indicative of one of the choicesof corrective optics.

The directional indicator may include a relatively light dot inside adark area, or vice-versa, a bar or other in-plane rotationallyasymmetric polygon, an arrow, a line, or another in-planerotationally-dependent object, or combinations thereof. The directionalindicator may be configured to be displayed to the test subject in atleast two configurations each uniquely indicative of one of the choicesof corrective optics. The directional indicator may include a white dotinside a black area, such that the white dot is movable to certainpositions each demonstrating a certain direction corresponding to one ofthe choices of corrective optics.

The directional indicator of the viewing target may be adjusted on adisplay using a machine coupled with a display during a visual acuitymeasurement of a test subject.

The method may include determining the visual acuity of the test subjectbased on choices received during the visual acuity measurement using acalculator or look-up table, or both.

To prevent accommodation, the viewing target may be displayed for 0.4seconds or less through a first corrective optic having more minussphere than a second corrective optic to be displayed of the at leasttwo choices of corrective optics. The viewing target may be displayedthrough the second corrective optic for longer than through the firstcorrective optic, after which the display of the first and secondcorrective optics may be repeated one or more times during the visualacuity measurement.

A method of self-guided refraction testing is also provided, includingproviding a directional indicator in a viewing target. At least twochoices of corrective optics are presented from a refraction unit to atest subject while looking at the viewing target. The presenting of eachof the optics is synchronized to one of the directions suggested by thedirectional indicator. A directional choice is received from the testsubject. The directional choice of the test subject is applied inselecting a next move of the refraction procedure.

The method may include communicating the directional choice of the testsubject to control a next move in presenting corrective optics to thetest subject. The communicating of the test subject's directional choicemay include, but is not limited to, use of a computer program, use ofelectronics, an electronic device and/or electronic circuits, use of aremote control unit using radio frequencies or infrared rays, or use ofhard wiring connections, or combinations of the above. The test subjectmay perform the self-guided refraction testing without human assistance.Furthermore, the computer program may provide voice guidance to the testsubject, and/or may receive voice inputs from the test subject.

The method may include receiving a further directional choice of thetest subject between a different set of corrective optics in refining anoptimal end point of refraction. The further directional choice of thetest subject may include a reverse direction than a previous answer. Asearch step size may be reduced before executing a correspondingdirectional move.

A self-guided refraction device is also provided including an adjustableoptical system, a display for presenting a viewing target including anadjustable directional indicator disposed along an optical path such asto be viewable through the adjustable optical system by a test subject,a computer coupled with the display and configured to synchronizeadjustment to the corrective optics and directional indicator based oninputs received from the test subject, and one or more non-transitorycomputer-readable media having code embedded therein for programming thecomputer to control any of the methods described herein.

A method of refracting a test subject is also provided that includeschoosing a starting point, and presenting a viewing target. A searchstep size is determined, as is a bracketing step size. The bracketingstep size is equal to or greater than the search step size. A centerposition is located that is at least two times the search step size fromthe starting point. A test subject is presented with at least twochoices of corrective optics. The two choices are at center positionplus bracketing step, and at center position minus bracketing step. Oneof the choices is closer to the optimal end point than the other choice.The method includes receiving from test subject an indication of whichpresentation is better in quality of image of the viewing target. A timebetween the presenting and the receiving is recorded. The methodincludes moving to a new center position by one search step towards theoptimal end point. The method repeats these steps confirming that thetime required to make a decision continues to increase, until the testsubject can no longer tell which of the two choices is better in imagequality.

A method of refraction suppressing an accommodative response during avisual acuity measurement is also provided. The method involvescontrolling duration of presentation of two choices of correctiveoptics. The duration of presentation of the more minus sphere power isset to be less than 0.4 seconds. The duration of presentation of theless minus sphere power may be set to more than 0.4 seconds.

One or more non-transitory computer-readable media having code embeddedtherein for programming one or more processors to perform any of themethods described herein.

A refraction device is also provided for determining a visual acuity andproviding corrective optics for a test subject. The device includes anadjustable optical system, a computer, and a display including anadjustable viewing target disposed along an optical path such as to beviewable through the adjustable optical system by a test subject. Thecomputer is programmed to perform or assist in the performance of any ofthe methods described herein.

Several embodiments are described that provide refraction tests that areintuitive, and may be administered with minimum teaching or learning inthe sense that they generally do not require complicated logic ormemorization. A directional indicator is generally provided in a viewingtarget. An example of a directional indicator is schematicallyillustrated at FIGS. 1(A) and 1(B). The directional indicator of FIGS.1(A) and 1(B) includes a relatively light (e.g., white) dot 110, withina dark (e.g., black or blue) circular area 120. The dot 110 may bedistinguishable from the area 120 in many ways, including havingdifferent colors or grayscale values, or the dot 110, which may have anyarbitrary shape, may protrude from the area 120 which may also have anyarbitrary shape. The area 120 is optional, as the “dot” 110 may have adirectional shape, e.g., that is rotationally dependent such as an arrowor any rotationally asymmetric shape, character, symbol, polygon,indicator, letter, number, curved line or shape, or otherdistinguishable object.

In the example of FIG. 1(A), the white dot 110 is at a “top” position,while in FIG. 1(B) the white dot 110 is at a “bottom” position. Thetiming of the location of the white dot, at either the top or bottomposition, is dynamically linked to the presentation of the lenses, orthe optics, as the test subject is looking at the viewing target throughthese optics. In another example, an arrow may point up corresponding tothe position of the white dot in FIG. 1(A) or the arrow may point downcorresponding to the position of the white dot in FIG. 1(B), or thearrow may point right and left, or Superman may be flying up or down, orany other directionally-definitive combination.

Most of a refraction test involves a search for an optimal correctivelens. Therefore, in the process of a search, a quality of vision maybecome improved, stay the same or become worse. An example isillustrated in FIG. 2. The curve represents change of sphere power inthe x axis, and the corresponding visual acuity (VA) level in they-axis. In this example, the test subject has the best VA of 20/20 at−2.25 D. In this example, the patient is 70 years old and has zeroaccommodation power. The lenses may be motor driven, and a desiredsphere power may be presented to the test subject on demand. That is,once the test subject indicates better one or better two using an inputdevice in a way suggested by the directional indicator associated withthe choice of the test subject, then an advantageous refractionapparatus in accordance with certain embodiments automatically providesthe next choice based on the input received from the test subject. Usingthe example of FIGS. 1(A) and 1(B), if the first choice is associatedwith FIG. 1(A) and the second choice with FIG. 1(B), then the patientmay move a joystick up to select the first choice or down to select thesecond choice, or the patient may click a mouse with the cursor over anupper object for the first choice or a lower object for the secondchoice.

Since the refraction process described here is intuitive in nature, itcan be performed by a test subject alone, or it can be conducted by athird party person. A computer program may provide voice guidancethroughout the refraction process. It may also perform a communicationfunction, receiving input from the test subject, which is derived fromits directional choice, sending that to an optical system, adjusting thedirectional indicator and synchronously presenting corrective optics fora test subject to look through while looking at the viewing target.

Referring to FIG. 2, in an example refraction process, a −1.75 D lensmay be first presented along the line of sight of the test subject. Thismay provide a VA of 20/32 as illustrated at 210 of FIG. 2. The nextpresentation 220 in this example is a −2.0 D lens that is provided. Inaccordance with certain embodiments, the lens 210 at −1.75 D ispresented at the same time as a directional indicator, e.g., such asthat of FIG. 1(A), where the white dot 110 is displayed in the “Top”position within the disk 120. The presentation duration may be chosenfrom 0.3 seconds to 1.5 seconds, or even 5 seconds or more. In certainembodiments described in more detail below, the more negative sphere ispresented for 0.4 seconds or less to avoid accommodation, while the morepositive sphere may be presented longer. Next, a lens at 220 in FIG. 2,at −2.0 D, is presented. The directional indicator of FIG. 1(B) ispresented at the same time as this second lens choice, i.e., the whitedot 110 moves to the “bottom” position within the disk 120 (or the arrowflips to point down, etc.). That is, the directional indicator changesfrom FIG. 1(A) to FIG. 1(B) synchronously with the movement of lenspresentations from −1.75 D at 210 in FIG. 2 to −2.0 D at 220.

The presentations 210 and 220 may be repeated automatically until thetest subject makes a choice answer, e.g., in this case the “bottom”. Aninput device, such as a mouse, or a joy stick is provided to the testsubject. Sound may also be used such as a computer program trained todistinguish “the first one” from “the second one” when the test subjectspeaks his or her choice. The test instruction may be quite simple,e.g., if the quality of the image is better when the dot is at the topposition, move the joy stick towards the “top”, or roll the mouse wheelup by one click, or push the joy stick away from the test subject orspeaks certain words that a microphone coupled to a machine can pick up.Likewise, if the image when the dot is at the bottom is more sharp andfocused, move the mouse wheel or the joy stick towards “bottom”, ortowards the test subject. These instructions are simple and intuitive asintended for broad application. A trigger button at the end of a joystick may be used as an indication when the two presented images areclose to being equal or there may be a third “equal” choice otherwiseprovided. In the case of using a mouse, an “equal” may be indicated bypushing both the left and right clicks at the same time or just theright click or by putting the cursor neither over the first or secondchoices and clicking.

In the example of the mouse wheel, after one click down, indicating thatthe test subject prefers 220 over 210 in FIG. 2, a computer program mayautomatically instruct a processor to present 220 and 230 as the nexttwo choices, e.g., with more positive power having the directionalindicator of FIG. 1(A), e.g., the white dot at the top position, again.In this case, 230 at −2.25 D of FIG. 2 provides the best vision for thetest subject as illustrated. The exemplary mouse wheel input device ismoved one click down indicating image at 230 is better than 220 for thistest subject. In the next presentation 230 may be presented against 240.This time the test subject should pick 230 over 240, e.g., by rollingthe mouse wheel upward, indicating that he or she prefers the image whenthe dot is at the top. The computer is programmed to recognize that themouse direction has been reversed, and concludes that an optimal acuityend point has been reached at 230.

In this example, no human operator needed to once ask “better one orbetter two?” nor does an operator need to present choices repeatedly toseek an answer from the test subject. The entire sphere lens search maybe performed entirely self guided by the test subject with theassistance of an advantageously configured machine. Another aspect of aself-guided refraction procedure in accordance with certain embodimentsis that test subject may provide input or answers to the refractioncomputer program, without taking his or her eyes off the test target.

Viewing Target

In FIG. 3 (A), a directional indicator in accordance with certainembodiments is modified from that illustrated at FIGS. 1(A) and 1(B) toinclude a series of thin lines emanating from the disk 110 (or otherarbitrary shape). A detailed description of such a viewing target isprovided in contemporaneously-filed patent application by Shui Lai,entitled “Effective Acuity and Refraction Targets” which is incorporatedby reference. Such target has higher sensitivity than a typical Snellenletter eye chart, and has other benefits including reducing a likelihoodof over-minusing. Another refraction target is illustrated at FIG. 3(B),where a row of Snellen letters are presented. Disposed in the middle ofthe row of letter is the directional indicator of FIGS. 1(A) and 1(B).The exact location of the directional indicator is not a limitingfactor, as it can be placed anywhere within the viewing angle of thetest subject. However, it may be easier for the test subject if it isplaced in the midst of a viewing target, as in the examples of FIGS.3(A) and 3(B). In one embodiment, the letter size displayed in FIG. 3(B)may be adjustable electronically or manually.

Adjustable Optical System

An instrument may be used that is capable of presenting and changing toa specified lens power via motor control. One such instrument isdescribed in a patent by the same inventor, Shui Lai, which is U.S. Pat.No. 7,726,811, entitled “Subjective Refraction Using ContinuouslyVariable Zernike Wave Plates” and is incorporated by reference.

In such an instrument, the spherical power may be adjustable by moving alens in a spherical adjustable assembly, or SAS. The lens may be movedin a linear dimension, e.g., riding on low friction rails. The latencytime may be about 50 milliseconds for a 0.5 diopter movement orsomewhere between 1-10 ms and 100-500 ms. The astigmatism power may alsobe adjustable by counter-rotating a pair of pure astigmatism opticplates. The full power range can be scanned through a 45 degreerotation. The latency of the astigmatism for a 0.5 diopter change mayalso be in a range around 50 milliseconds such as between 1 ma and100-500 ms. The response time of such device can be improved by usinglighter materials and smaller optics, and somewhat longer response timesmay be tolerated. That is, neither the 50 millisecond response time northe described ranges are limiting factors.

Other methods of making lens power changes can be adapted in furtherembodiments, without limitation. For example, a fluid lens such thosedescribed in U.S. Pat. Nos. 4,477,158, 4,953,956 can also be used here,and as such these patents are incorporated by reference. Since the lenspower may be achieved through injecting or removing fluid in a confinedvolume, these have the advantage of having fewer or no moving mechanicalparts. Piezoelectric actuators can be used in the pumping mechanism toimprove the response time of the fluid lens power change.

Another example of a fast power acting lens is a liquid crystal waveplate device, such as those described in U.S. Pat. No. 4,601,545, whichis incorporated by reference. By changing the optical path difference ofthe wave plate in a manner simulating that of a spherical power lens,one may make such liquid crystal device to behave just like a lens. Adrawback of liquid crystal lens however is its limited power range.Since the power difference in the two presentations is about 0.5 D,liquid crystal lenses are well suited to be used in certain embodimentsto provide a power difference. In the example of FIG. 2, a liquidcrystal lens may be added to a traditional phoropter, or any suitabledevice, including one in U.S. Pat. No. 7,699,471 by Shui Lai, which isincorporated by reference. The phoropter lens power may be set in themiddle between the presented powers. For example, if one were to present220 and 230 of FIG. 2, then the phoropter could be set in the middle, orat −2.125 D. The liquid crystal lenses can provide the added differenceof +0.125 D at the top position, and −0.125 D at the bottom position.

Controlling Accommodative Response in a Refraction Test

In certain embodiments the time duration of the presentation of arefractive target to a patient under examination is controlled tocurtail accommodative response. The dynamic nature of the targetpresentations may be manipulated in such a way as to produce desirableeffects, such as eliminating over-minus, and arriving at more accurateend points quickly.

A test subject who is a young person will have accommodative power inhis or her eye. A viewing target such as that illustrated at FIGS. 1(A)to 1(B), or the modified Snellen eye chart of FIG. 3(B), for example,may be presented to the test subject. In this case, if the presentationsof 230 and 240 in FIG. 2 are both one second or longer, then due to theaccommodative response of this test subject, the quality of the image at−2.5 D now may look the same as at 230 following the accommodation curve260, or having almost the same acuity at 245 or 280, compared with thechanges presented at 240 or 250 not impaired by accommodation. That is,at 245 and 280 an elevated acuity level is the result of accommodationinto an over-minus region. Worse than that, once the accommodativeresponse is triggered, the young test subject may even say that 245 ismore focused than 235, where the acuity actually appears to have droppedfrom 230 on the real curve 200 to 235 on the accommodated curve 260, dueto the extra plus power at the test subject's natural lens.

Recognizing the existence of accommodative response, a process inaccordance with certain embodiments controls it. An accommodativeresponse takes about 0.3 to 0.4 seconds for the natural lens to add theextra plus power to make over-minus vision appear to be sharp andfocused. Thus, a dynamic presentation method may be used which limitsthe presentation time period to be equal to or less than theaccommodative response time. For example, when −2.5 D at 245 of FIG. 2is presented as the more minus power choice when the other choice is−2.25 D at 230, then the −2.5 D power is provided for 0.4 second orless. Used as an example, the presentation at −2.5 D may be set to 0.4seconds, 0.3 seconds, 0.2 seconds or 0.1 second, and that of −2.25 D maybe set higher, e.g., to 1 second. When the two lenses power arepresented repeatedly at the respective time durations, e.g., 1 secondand 0.3 seconds, the dot of FIGS. 1(A) and 1(B) jumps between the topand bottom positions (or an arrow flips up and down, etc.), synchronizedwith the presentation of changing optics.

The presentation period of the more positive sphere power may beintentionally set at a time much longer than the accommodative responsetime of 0.4 or 0.3 seconds, or it may be the same or similar duration.The viewing time may favor the more positive power presentation of −2.25D. Therefore, even for this test subject, −2.5 D presentation remains tobe at the 240 acuity level of FIG. 2, and not at 245 with accommodativeresponse. In this way, reduction or elimination of over-minusing isprovided using a dynamically linked viewing target with a proper choiceof presentation time, and synchronization between the target and theoptics. In this case the test subject identifies 230 at −2.25 D as beingmore focused than 240 at −2.5 D. The lens power at 230, at −2.25 D isthen determined to be the optimal power for this test subject.Over-minusing conditions have been prevented in this example.

The sphere powers used in the example above are also not limitingfactors. The test subject may have other values as his or her finaloptimal sphere power not affecting the benefits and working principlesof the advantageous process. Also, neither the incremental power changeof 0.25 D, nor the acuity level of the test subject, as illustrated inthe y-axis of FIG. 2 are limiting factors.

The lens power modulator can be achieved using a liquid crystal lens, afluid lens (or liquid cell lens), or a continuously adjustable phoropteras in the instrument described for example in the earlier-cited patentsby Shui Lai.

In FIGS. 1(A), 1(B), 3(A) and 3(B), the circular area 120 with dot 110are used as non-limiting examples, and use of the top and bottompositions in that example indicator is itself an example. That is, thedot positions may be right and left, instead of top and bottom. In suchcase, the accompanying instructions might include “move the joy stick tothe right if the image appears sharper and more focused when the dot ison the right, and move the joy stick to the left, if the image appearssharper when the dot is at the left position.” In this case, the mousewheel may not work as well, since the test subject has to remember, leftis to move the mouse wheel up one click, left to roll the mouse wheeldown one click, but user-preferences may be selected. Instead of jumpingdots, one could use an arrow that changes pointing directions up anddown, either by itself or within the circular area 120 or protruding outof the circular area 120. An up arrow would suggest to move the mousewheel up one click, and a down arrow to move the mouse wheel down oneclick, etc.

One advantage of certain embodiments is that the directional indicatormay be relatively small and can be seen centrally without rolling theeye ball, or its gaze angle. Likewise, when a letter in FIG. 3(B) isbeing looked at, the jumping dot in the circular area is within the“peripheral vision” of the stare. It is advantageous to provide a quickdetermination whether the quality of the vision is better or worse atone of the two dot positions, without taking the eye off the letter thetest subject is staring at.

Bracketing Method to Find the Optimal End Point

The above-described embodiments involved finding a refraction end pointin searching for an optimal sphere power by locating a best qualityimage as an optimal end point, or at a sharpest focus point. Anothermethod is to find the best “bracketed” locations as the end point. Inthis method, slightly blurred images are provided and the test subjectis asked to compare his or her degree of blurriness. At the end point,the quality of image is not at it sharpest focus, but rather, the twopresented views are close to being equally blurred.

This method is particularly advantageous for finding an optimal endpoint where there is no hazard involving accommodative response when apresentation is at a position after passing the optimal point, similarto the over-minusing conditions in finding the optimal sphere value.Therefore, this method is particularly advantageous when searching foraxis angle and the power of the optimal cylinder.

We illustrate this method in FIG. 4, in a search of an optimal axisangle at a given cylinder power. Like FIG. 2, the acuity level is in theY axis, and in this case, the axis angle is in the X axis, unlike FIG. 2which has the sphere power in the x-axis. A relation curve is shown FIG.4 to illustrate how acuity may vary with the axis angles. Each of thepoints 410, 420, . . . , to 480 may be separated by, e.g., 5 degreesaxis angle from each neighboring point. The difference in acuity levelis recognized herein as not being the same as the axis angle variesacross the curve from 410 to 420, as compared to from 430 to 440. Infact the acuity level difference between 410 and 420 may be greater by afactor of two as these neighboring points are farther away from theoptimal region than those at points 430, 440, and 450. From here on, weuse the definition of VA(410), to mean the visual acuity level of thetest subject when the optics are presented to him or her at axis angleposition 410 in FIG. 4. For example, VA(410)-VA(420) is 1.5× to 2× ofVA(430)-VA(440). Likewise comparisons can be made between the VA(450)-VA(440), and the previous two sets of neighboring points, and soon. It is recognized herein that it is not effective to find an optimalend point by comparing the nearest neighbor points. Instead, a largerbracket size may be advantageously used in accordance with certainembodiments, while maintaining a small nearest neighbor step size in theend point search.

As an illustrative example, if one starts at point 430 in FIG. 4, twochoices may be presented at 410 and 450. If a directional indicatortarget in accordance with certain embodiments is used, then the viewingtarget may be viewed with axis angle 410 and FIG. 1(A), while the acisangle 450 may be viewed with the indicator FIG. 1(B). Whether or not adirectional indicator is used in this embodiment, the test subject isasked to determine of 410 and 450 provides a sharper image. Thesensitivity may be increased by a factor of 8, for example, as comparedto presenting point 440 and point 450. That is, a test subject can moreeasily pick 450 by moving an input device per bottom indicator of FIG.1(B) to indicate that the viewing target is sharper and more focusedthan the 410 choice. In this case, the center point is the 430, and thebrackets are 2 times the nearest neighbor step size.

Since the test subject determined at this step that the “bottom” (FIG.1(B)) choice 450 is more focused, he or she may roll the mouse wheeldown by one click, or otherwise indicate the choice of 450 over 410. Thenew center position would be moved towards 450 to be now 440, forexample, for a next step in the test. This move of one nearest neighborstep may be referred to as a mouse move step size. By this definitionthe brackets are +/−2 mouse move steps, centering at 440, in this case.The test subject will now compare a viewing target at 420 to one at 460.Again, it should be an easy choice for the test subject who would answer“bottom” choice or that suggested by directional indicator of FIG. 1(B).

Then next, point 430 is compared to 470, and the center point is at 450,the supposed optimal point in this example. Now the acuity level ofthese points should be about equal, and test subject might say orindicate, “Equal”, such that the optimal end point is obtained.

Timing for Test Subject's Response

This test is easier when the center point is farther from the optimalend point. For example, in the last example, when the test started at430, the difference of image quality between 410 and 450 which is thepresumed optimal end point, is very obvious to the test subject. As anaside, one may use an arbitrary scale on the Visual Acuity (VA) axis,and shift the zero to VA(410) a illustrated in FIG. 4. Relative valuesmay be assigned to the corresponding points for VA(420), VA (430), etcas illustrated. The point is that the exact value for each of the VApoints is not critical, but rather the goal is to determine changes ofthe VA values which become smaller and smaller until the center pointbecomes the optimal end point, which is this example is at 450 and VA=10(a.u.).

Now, at the start of this example test, the center point was at 430, andthe difference of image quality, VA(450)-(410)=10 units as shown in FIG.4. Next the center point is moved to 440, the image quality in acuity isVA(460)-(420)=9−4=5, or half the difference of the previous step. Thenext mouse click moves the center position of the bracketing to 450, nowthe difference in image quality is zero. It is recognized herein thatthe test subject would find it easier to answer when the center point isat 430, than when at 440, and would find it very hard to tell which ofthe two is actually better at 450. This “degree of easiness” of choiceis used to find the optimal end point, i.e., when the choice is toughestthen the center point is the optimal endpoint.

A self-guided refraction test machine, e.g., a computer or otherprocessor-based device, may be used to monitor a time duration for thetest subject to give an answer after each new center position. Forexample, the test subject may only need 1 to 2 jumping dot periods toanswer when the center position is at 430, and may need 3 to 4 jumpingdot periods to answer when the center is at 440, and he or she may takeup to 5 periods or more to decide that he or she actually cannot tellwhether the top or the bottom is more focused when the center is at 450.Also, in a self guided refraction test in accordance with certainembodiments, the number presentation periods may be recorded. The testmay also take into account that an optimal end point is approached whenthe test subject is taking increasingly longer times to provide answers.If an answer cannot obtained after 10 periods, for example, the programcan actually decide to pick that as an “Equal” for the test subject.

Auto Refinement on Reversing

If in the last example, the optimal end point is not at 450, but rathersomewhere between 440 and 450, then the test subject may say “the topposition is slightly more focused.” Now we have a reversing situation,namely when the center position was at 440, patient asked for “bottom”,but when the optics were moved to 450, he asked for “top”. The computerprogram can repeat itself between these two central positions and runitself into a repeat loop. An auto refinement algorithm may be providedwherein when a reversing situation occurs, the mouse move step size isreduced by a factor of 2, before it executes a command to move a steptowards “top”. Now a move towards “top,” effectively moves the centerposition to the middle of 440 and 450. If the test subject confirms thisis the optimal end point, and answers “Equal”, then the angle search inthis case is finished. However, if further reversing occurs, autorefinement can continue to sub-divide the mouse move step size by afactor of 2 in each reversing until a final end point is reached.

The search step may be in the increments of the nearest neighbor pointstep, while the brackets may be at two times the neighboring pointdistance. The end results may be increased sensitivity in the test, andmore certainty in the finding the end point, without compromising searchstep accuracy.

For a search over a larger region of angles, one may use a speedysearch. The mouse steps and the bracketing steps may be increased by afactor of 2, for example. The speedy search may be increased by a factorof two, but the accuracy may be compromised with the rougher search stepsize. However, once a rough optimal end point has been established, themouse step may be reduced as well as the bracketing step by, e.g., afactor of 2, or may be set forth and described in the auto refinementprocedures. A general approach may be to find the general vicinity nearthe optimal end point using quick and larger steps, and then to refinestep size to fine tune to the approximately exact end point.

The bracketing method is also applicable for a search of optimalcylinder, or astigmatism power. One would have to replace the axis anglelabel in the X axis in FIG. 4 with an astigmatism power, rather thanaxis angles, and then the rest of the methods, including bracketing,timing of answers, and auto refinement, apply.

Example Self Guiding Refraction Procedure

FIG. 5 illustrates a self guided refraction procedure. At box 510, thestart of refraction, a starting point is chosen. The starting point canbe selected with the aid of an autorefractor, wavefront aberrometers, ora retinoscope, or a previous measurement, or an starting arbitrary pointmay be used. These values may be either manually or electronicallypopulated from a electronic medical record software.

Next, at box 520, an operator may choose to start finding a sphere, axisangle, or the power of a cylinder end point. The flow chart may beapplied to any or all of the three cases. A viewing target including adirectional indicator may be selected or assigned, and used, such asillustrated in the examples of FIGS. 1(A), 1(B), 3(A) and/or 3(B), or anarrow that flips, or otherwise.

At box 530, a white dot is moving synchronously in a directionalindicator, e.g., as illustrated at FIGS. 1(A) and 1(B). Twopresentations (or dual presentations) may be used, where optics settingsmay switch between +/− bracketing values from a center position. Theycan be two axis angles of fixed astigmatism optics, or two spherevalues, or two astigmatism diopter settings.

At box 540, a test subject may provide an answer after a presentationhas been repeated a number of times. The time lapse may be recorded fromthe start of optics presentations to the test subject to the time ofreceipt of an answer/choice by the test subject.

At box 550, if the answer is either a “Top” (FIG. 1(A) or similar) or a“Bottom” (FIG. 1(B) or similar), then the process can branch at 550 tobox 560. Otherwise, at box 570, when the answer at 540 is “Equal” or noanswer is given for a time longer than a predetermined time, e.g., asmay be fixed or adjusted from previous presentations, then the test maybe ended at box 575, and the optimal end point is the center positionbetween the two choices in the final presentation, or at the middlebetween the top and bottom presentation values.

From box 560 however, there is another query at 580 to check whether theanswer is in the reversed direction of the previous answered direction.Of course, if this is the first answer, or it is not a reversing answer,then the test continues to 585, then moves to the next center positionand back at 530 the optics are presented at a +/− bracketing valuesabout the new center value.

If it is a reversing from box 580, then the next query at 590 is todetermine if the measurement is for sphere value 592, or if it is foraxis angle or astigmatism at box 595. If it is for sphere, then at box594 the test is finished and the optimal end point for the sphere is thevalue at the “Top” optics position.

If reversing occurs with axis angles or astigmatism power, then from box595, the process moves on to box 597 where a refinement of the mousemove step size is made, and to the bracketing step size, e.g., both maybe reduced by a factor of 2. A mouse click execution input may bereceived in accordance with the patient response from Box 560, i.e., topor bottom. Then, the process continues back to box 530 at the new centervalue, and new bracketing values, and continues with the flow chart.

The described embodiments are merely illustrative and the invention isnot limited to the specifically-described examples. Instead, theinvention is set forth in the claims and includes structural andfunctional equivalents thereof.

1. A refraction device for determining a refraction end point andproviding corrective optics for a test subject, comprising: (a) anadjustable optical system providing corrective optics to the testsubject; and (b) an adjustable viewing target disposed along an opticalpath such as to be viewable through the adjustable optical system by atest subject, and (c) wherein the adjustable viewing target comprises adirectional indicator linked synchronously to at least two choices ofcorrective optics presented to the test subject.
 2. The refractiondevice of claim 1, comprising an input device configured to becontrolled by a test administrator to execute a move in a refractionprocess in accordance with a direction suggested by the directionalindicator which is selected by the test subject, while the test subjectselects between the at least two choices of corrective optics.
 3. Therefraction device of claim 2, wherein the test administrator is eitherthe test subject, a third party person.
 4. The refraction device ofclaim 2, wherein the direction suggested by the directional indicatorcorresponds to a corrective optics choice for the next move of therefraction process, approaching an optimal refraction end point.
 5. Therefraction target of claim 1, wherein the adjustable viewing target isadjustable to at least two configurations each uniquely indicative ofone of the choices of corrective optics.
 6. The refraction device ofclaim 1, wherein the directional indicator comprises a relatively lightdot inside a dark area, or vice-versa, a bar or other in-planerotationally asymmetric polygon, an arrow, a line, or another in-planerotationally-dependent object, or combinations thereof, and isconfigured to be displayed to the test subject in at least twoconfigurations each uniquely indicative of one of the choices ofcorrective optics.
 7. The refraction device of claim 6, wherein thedirectional indicator comprises a white dot inside a black area, andsuch that the white dot is movable to certain positions eachdemonstrating a certain direction corresponding to one of the choices ofcorrective optics.
 8. The refraction device of claim 1, furthercomprising a machine coupled with a display displaying the viewingtarget, and configured to adjust the viewing target during a visualacuity measurement of a test subject.
 9. The refraction device of claim8, further comprising a calculator or look-up table, or both, fordetermining the visual acuity of the test subject based on the visualacuity measurement.
 10. The refraction device of claim 1, wherein toprevent accommodation the device is configured to display for 0.4seconds or less a first corrective optic having more minus sphere than asecond corrective optic to be displayed of the at least two choices ofcorrective optics.
 11. The refraction device of claim 10, wherein thesecond corrective optic is configured to be displayed after the firstcorrective optic for longer than the first corrective optic, after whichthe display of the first and second corrective optics is repeated one ormore times.
 12. A refraction method comprising: (a) providing correctiveoptics for a test subject; (b) adjusting an optical system to a firstconfiguration for the test subject to view through a first correctiveoptic a viewing target including a first directional indicator; (c)adjusting the optical system to a second configuration for the testsubject to view through a second corrective optic the viewing targetincluding a second directional indicator; (d) receiving a directionalinput in accordance with the first or second directional indicator fromthe test subject uniquely indicating a choice of one of the first andsecond corrective optics; and (e) presenting one or more furtherconfigurations of corrective optics for the test subject to choosewherein the presenting of further configurations of corrective optics isdirected by the choice, until a prescriptive recommendation isdetermined.
 13. The refraction method of claim 12, wherein the receivingof the directional input comprises receiving a signal from an inputdevice controlled by the test subject to indicate a direction suggestedby the directional indicator for selecting between the first and secondcorrective optics.
 14. The refraction method of claim 13, furthercomprising presenting to the test subject the choice between the firstand second corrective optics in accordance with unique directions eachsuggested by the directional indicator as corresponding to one of thefirst and second corrective optics.
 15. The refraction method of claim12, further comprising adjusting the directional indicator of theviewing target to at least two configurations each uniquely indicativeof one of the choices of corrective optics.
 16. The refraction method ofclaim 12, wherein the directional indicator comprises a relatively lightdot inside a dark area, or vice-versa, a bar or other in-planerotationally asymmetric polygon, an arrow, a line, or another in-planerotationally-dependent object, or combinations thereof, and isconfigured to be displayed to the test subject in at least twoconfigurations each uniquely indicative of one of the choices ofcorrective optics.
 17. The refraction method of claim 16, wherein thedirectional indicator comprises a white dot inside a black area, andsuch that the white dot is movable to certain positions eachdemonstrating a certain direction corresponding to one of the choices ofcorrective optics.
 18. The refraction method of claim 12, furthercomprising adjusting the viewing target on the display using a machinecoupled with a display during a visual acuity measurement of a testsubject.
 19. The refraction method of claim 18, further comprisingdetermining the visual acuity of the test subject based on choicesreceived during the visual acuity measurement using a calculator orlook-up table, or both.
 20. The refraction method of claim 11, whereinto prevent accommodation, further comprising presenting the viewingtarget for 0.4 seconds or less through a first corrective optic havingmore minus sphere than a second corrective optic to be displayed of theat least two choices of corrective optics.
 21. The refraction method ofclaim 20, wherein the second corrective optic is displayed after thefirst corrective optic for longer than the first corrective optic, afterwhich the display of the first and second corrective optics is repeatedone or more times.
 22. The refraction device of claim 1, furthercomprising one or more non-transitory computer-readable media havingcode embedded therein for programming one or more processors to performor assist in the performance of a refraction method, and to determinevisual acuity of the test subject.
 23. The refraction method claim 12,wherein one or more non-transitory computer-readable media having codeembed therein for programming one or more processors to perform orassist in the performance of a refraction method, and to determinevisual acuity of the test subject.
 24. A method of self-guidingrefraction testing, comprising: providing a directional indicator in aviewing target; presenting at least two choices of corrective opticsfrom a refraction unit to a test subject while looking at the viewingtarget; synchronizing the presenting of each of the optics to one ofdirections suggested by the directional indicator; receiving adirectional choice from the test subject; and applying the directionalchoice of the test subject wherein the directional choice selects a nextmove of the refraction procedure approaching the test subject's optimalrefraction end point.
 25. The method of claim 24, further comprisingcommunicating the directional choice of the test subject to control anext move in presenting corrective optics to the test subject, whereinthe communicating is performed by a computer program, electronics,remote control, or hard wiring connections, or combinations thereof. 26.The method of claim 24, wherein the test subject performs theself-guiding refraction testing without human assistance.
 27. The methodof claim 24, further comprising: receiving a further directional choiceof the test subject between a different set of corrective optics inrefining an optimal end point of refraction, and wherein the furtherdirectional choice of the test subject comprises a reverse directionthan a previous answer, reducing a search step size before executing acorresponding directional move.
 28. A self-guiding refraction device,comprising: (a) an adjustable optical system; (b) a display forpresenting a viewing target including an adjustable directionalindicator disposed along an optical path such as to be viewable throughthe adjustable optical system by a test subject, (c) a computer coupledwith the display and configured to synchronize adjustment to thecorrective optics and directional indicator based on inputs receivedfrom the test subject; and (d) one or more non-transitorycomputer-readable media having code embedded therein for programming thecomputer to control a method of self-guiding refraction testing, whereinthe method comprises: providing the adjustable directional indicatorwith the viewing target on the display; presenting at least two choicesof corrective optics from a refraction unit to a test subject whilelooking at the viewing target on the display; synchronizing thepresenting of the corrective optics to directions suggested by theadjustable directional indicator; receiving a directional choice fromthe test subject; and applying the directional choice of the testsubject wherein the directional choice selects a next move of therefraction procedure approaching the test subject's optimal refractionend point.
 29. The device of claim 28, wherein the method furthercomprises communicating the directional choice of the test subject tocontrol a next move in presenting corrective optics to the test subject,wherein the communicating is performed by a computer program,electronics, remote control, or hard wiring connections, or combinationsthereof.
 30. The device of claim 28, wherein the test subject performsthe self-guiding refraction testing without human assistance.
 31. Thedevice of claim 28, wherein the method further comprises: receiving afurther directional choice of the test subject between a different setof corrective optics in refining an optimal end point of refraction, andwherein the further directional choice of the test subject comprises areverse direction than a previous answer, reducing a search step sizebefore executing a corresponding directional move.
 32. A method ofrefracting a test subject comprising: (a) choosing a starting point, (b)presenting a viewing target, (c) determining a search step size, and abracketing step size, the bracketing step size being equal to or greaterthan the search step size. (d) locating a center position that is atleast two times the search step size from the starting point, (e)presenting at least two choices of corrective optics for the testsubject, the two choices being at center position + bracketing step, andat center position − bracketing step, wherein one of the choices iscloser to the optimal end point than the other choice, (f) receivingfrom test subject an indication of which presentation is better inquality of image of the viewing target, (g) recording a time between thepresenting and the receiving, (h) moving to a new center position by onesearch step towards the optimal end point, (i) repeating steps (e), (f),(g) and (h), confirming that the time required to make a decisioncontinues to increase, until the test subject can no longer tell whichof the two choices is better in image quality.
 33. A method ofrefraction suppressing an accommodative response during a visual acuitymeasurement, comprising controlling a duration of presentation of twochoices of corrective optics, wherein the duration of presentation ofthe more minus sphere power is set to be less than 0.4 seconds.
 34. Themethod of claim 33, wherein the duration of presentation of the lessminus sphere power is set to more than 0.4 seconds.
 35. A refractiondevice for performing a refraction test and providing corrective opticsfor a test subject, comprising: an adjustable optical system; acomputer; and a display including an adjustable viewing target disposedalong an optical path such as to be viewable through the adjustableoptical system by a test subject, and one or more non-transitorycomputer-readable media having code embedded therein for programming thecomputer to perform a method of refracting a test subject, wherein themethod comprises: choosing a starting point, presenting a viewingtarget, determining a search step size, and a bracketing step size, thebracketing step size being equal to or greater than the search stepsize. locating a center position that is at least two times the searchstep size from the starting point, presenting at least two choices ofcorrective optics for the test subject, the two choices being at centerposition + bracketing step, and at center position − bracketing step,wherein one of the choices is closer to the optimal end point than theother choice, receiving from test subject an indication of whichpresentation is better in quality of image of the viewing target,recording a time between the presenting and the receiving, moving to anew center position by one search step towards the optimal end point,repeating the method confirming that the time required to make adecision continues to increase, until the test subject can no longertell which of the two choices is better in image quality.
 36. Arefraction device for performing a refraction test and providingcorrective optics for a test subject, comprising: an adjustable opticalsystem; a computer; and a display including an adjustable viewing targetdisposed along an optical path such as to be viewable through theadjustable optical system by a test subject, and one or morenon-transitory computer-readable media having code embedded therein forprogramming the computer to perform a method of refraction suppressingan accommodative response during a visual acuity measurement, whereinthe method comprises controlling a duration of presentation of twochoices of corrective optics, wherein the duration of presentation ofthe more minus sphere power is set to be less than 0.4 seconds.
 37. Thedevice of claim 50, wherein the duration of presentation of the lessminus sphere power is set to more than 0.4 seconds.
 38. One or morenon-transitory computer-readable media having code embedded therein forprogramming a processor to perform or assist in the performance of themethod of claim
 12. 39. One or more non-transitory computer-readablemedia having code embedded therein for programming a processor toperform or assist in the performance of the method of claim
 24. 40. Oneor more non-transitory computer-readable media having code embeddedtherein for programming a processor to perform or assist in theperformance of the method of claim 32.